Virtual reality (VR) systems and/or applications generally create a virtual environment for a user through a wearable headset and artificially immerse the user or simulate the user's presence in the virtual environment. To further allow user interaction with the virtual environment, technologies are being developed to allow the user to interact with the objects in the virtual environment. Positional information of the user is desirably detected and inputted into the VR systems and/or applications. For example, positional tracking methods may be used to track the position and/or movement of the user through tracking a trackable device (with a signal source such as a light source, etc.) attached to a part of user's body. For example, the trackable device can be a controller held in user's hand with a signal source which can be detected by a signal detector. In such instance, one or more controllers may be detected, identified, and/or tracked.
The trackable device includes a signal source. A tracking device can detect and capture the signal emitted by the signal source, and can accordingly track the movement of the trackable device based on the locations of the signal source. The signal source has a great range of varieties, such as a visible light source, an infrared light source, an ultraviolet light source, a millimeter wave source, etc. Each source has its own features with both strength and weakness. For instance, the trackable device may be exposed to an environment fulfilled with ambient lights. If a visible light source is chosen as a single source, it could be obfuscated by ambient lights such as sunlight, fluorescent lamp lights, or LED lights, which may affect the accurate detection and/or tracking of the device. Moreover, if there are ambient lights in the environment and the ambient lights are of the same color as the light emitted by the trackable device, it may become difficult for a camera to differentiate the trackable device from the background environment. As a result, the detection and the location of trackable device can become inaccurate. If an infrared light source is chosen, when there are multiple devices applied in the same scene, it would be hard to identify each device. Some solutions use multiple infrared-LEDs groups which twinkle in a pre-determined pattern, so each group has its particular pattern being able to be identified. Nevertheless, forming a twinkle pattern needs extra time and increases the total processing time, which would produces time delays and harm the user experience.